Gummy Smile

What Is Botulinum Toxin for a Gummy Smile?

Botulinum toxin for a gummy smile means injecting botulinum toxin into the muscles that pull the upper lip upwards, to temporarily reduce how strongly they contract when too much gum shows as you smile. In everyday language, this treatment is often called by the name of one product; the active ingredient is botulinum toxin type A. When the muscles contract less, the upper lip rises less when you smile and less of the gum is visible.

The idea behind the treatment is that, in this case, what reveals the gum is not the gum itself but the movement of the lip. The muscles most often targeted in studies are the muscle that lifts both the upper lip and the side of the nostril (levator labii superioris alaeque nasi), the upper lip elevator muscle (levator labii superioris) and the small cheekbone muscle (zygomaticus minor). In these studies, the dose was set according to how severe the gum display was. If the treatment is considered for you, the dose and injection points are your doctor’s decision, tailored to you.

An international expert consensus on the aesthetic use of botulinum toxin sets a clear criterion for considering it as a first option: the main cause of the appearance to be corrected must be excessive muscle contraction. The same consensus supports an approach that is based on the cause and tailored to the individual. Too much gum can also show for reasons other than the muscles, and in those cases the treatment does not meet expectations. Another botulinum toxin treatment for the upper lip, the Lip Flip, is described on a separate page.

RELATEDLip Flip

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What Does ‘Gummy Smile’ Mean?

‘Gummy smile’ is an English expression; in Turkish it is also called ‘dişeti gülüşü’ (‘gum smile’). Its medical name is excessive gingival display: more gum than usual showing above the upper front teeth when you smile.

There is no single threshold for when gum display counts as excessive. A review comparing surgical and non-surgical treatments used more than 2 millimetres of gum showing above the upper front teeth at the widest smile as its criterion. Other sources consider more than 3 millimetres aesthetically bothersome. Using different thresholds for the same concept shows that the definition itself rests on a consensus.

These thresholds are criteria used in research, not the definition of a disease. One study found that how gum display is perceived aesthetically differed significantly between different specialties within dentistry, and between specialists and non-specialists. The researchers drew attention to the subjective side of this judgement and stressed that the patient’s own perception should also be taken into account in planning. In short, gum showing when you smile is not, in itself, something that needs to be corrected; you decide whether or not it bothers you.

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Is the Cause Muscle, Bone or Teeth?

There is no single cause of too much gum showing. The causes are grouped as bone (skeletal), tooth-related and soft-tissue causes. They include:

• The upper lip rising too high when you smile.
• A short upper lip.
• Excess vertical growth of the upper jaw.
• Gums covering more of the teeth than usual.
• Gum overgrowth.
• Over-eruption of the front teeth.

Each cause has a different treatment.

Two conditions stand out among the soft-tissue causes: gums covering more of the teeth than they should (altered passive eruption) and a hypermobile upper lip (an upper lip that rises higher than usual when you smile). Their established surgical treatments are aesthetic crown lengthening and lip repositioning surgery, respectively. In other words, a cause in the soft tissue does not mean the cause is muscle-related.

How common each cause is depends on the population studied. In one of the studies carried out in different countries, the most common cause was gums covering too much of the teeth, and more than one cause was present in 44.3% of cases. In another study, this cause was found in 73.2% of participants, more than one cause was present in 55.3%, and having more than one cause was associated with more gum display. In a third study, excessive upper lip movement, alone or together with other causes, was the most common cause, at 68.2%.

In practice, this means that two smiles that look the same in the mirror can have different causes, and more than one cause is often present. That is why an approach based on the cause is recommended, combining more than one method in sequence when needed. The first question is not which treatment to have, but why the gum shows.

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Muscle-Related Gum Display

Botulinum toxin works when the gum display comes from overactive muscles that lift the upper lip. Reviews have found the treatment effective for gum display caused by overactive smile muscles; the same result is not expected when the cause is not muscle-related.

A meta-analysis (an analysis that combines the results of several studies) on the effect of botulinum toxin on gummy smile excluded patients whose cause was only gums covering too much of the teeth, thickened gums or over-eruption of the upper front teeth. When the cause is vertical excess of the upper jaw, jaw surgery is seen as the ideal solution; in borderline cases, and when the cause is excessive movement of the muscles that lift the upper lip, more conservative options can be considered.

The picture can also be mixed: a muscle-related component can occur together with another cause. In this area, botulinum toxin can also be used as a diagnostic aid, as a temporary solution or alongside other treatments. In a mixed picture, the toxin can affect only the muscle-related part of the appearance; the rest depends on the non-muscular cause.

The treatment does not give the same degree of result in everyone. In a study that followed patients treated with a standard dose, the size of the effect was linked to the severity of gum display at the start and to sex; according to the researchers, the result in these patients depended on these two factors more than on the cause or other factors. You can read how a problem of movement differs from a problem of volume in the article Botulinum Toxin or Fillers?.

RELATEDBotulinum Toxin or Fillers?

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Types of Gummy Smile and the Muscles Targeted

The gum does not show in the same area in every smile. One clinical study defined four types, based on where the gum shows and the muscles involved: the anterior type, with gum showing above the front teeth; the posterior type, with gum showing above the side teeth; the mixed type, where both are seen; and the asymmetric type, where the two sides differ. The researchers concluded that it is important to choose the injection technique according to the type and the muscles involved. However, this was a study of only 16 patients, with no sample size calculation and no statistical analysis.

The position of the muscles has been examined in cadaver studies. One anatomical study found that the attachment point of the upper lip elevator muscle was partly or completely covered by the other two muscles, and that the three muscles met in an area to the side of the nostril. The researchers proposed an injection point in an area close to the line of the three muscles, located using landmarks on the surface of the face, and made careful patient selection a condition.

There is no single view on how the treatment should be carried out. In a review of nine studies covering 269 patients, between one and three injection points were used on each side of the face, the muscles targeted varied from study to study, and no standard method emerged. So the most suitable approach appears to be one tailored to the person’s anatomy, smile type and the severity of their gum display. A double-blind, randomised trial (a trial in which participants are randomly assigned to groups and which treatment each person received is kept hidden) compared two different injection sites and found no difference in results between them.

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What Does the Research Show?

Research shows that botulinum toxin reduces gum display in the short term in muscle-related gummy smile. However, these studies are small; the products, doses and injection protocols used differ, and the results vary widely. So the available data do not give a definite picture of how large the effect will be or how long it will last, and they are not enough to predict any one person’s result.

A meta-analysis combining the results of 17 studies calculated an average reduction in gum display of 3.42 millimetres two weeks after treatment. In this analysis too, the variation between studies was very high; the researchers found the method effective particularly for gum display of up to 4 millimetres. Another meta-analysis also found a significant reduction at two weeks and at three months, but the results gradually decreased over time.

In an analysis of 13 prospective controlled studies, the greatest effect was seen two to four weeks after treatment. In another review covering nine studies, the average rate of improvement ranged from 24.85% to 99.65%, depending on the study. Such a wide range shows that no single result can be generalised to everyone.

Randomised trials are limited. In one double-blind, randomised trial, both of the injection sites compared were found to be usable. In another randomised trial comparing the number of injection points, using more points made the effect last longer, not stronger; however, because a high number of patients dropped out of follow-up, the researchers treated this result as a preliminary finding. As one of the reviews stressed, randomised controlled trials are needed for the treatment to become more systematic.

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When Does It Start to Work, and How Long Does It Last?

The effect does not appear immediately after treatment, and it is not permanent. According to reviews, a clear effect appears in the first weeks and then gradually fades; in most studies, gum display moved back towards, or returned to, its starting level over time. How long the effect lasts varies from study to study.

According to one review, the effect usually appears between the first and second week. The 17-study meta-analysis reported that the effect lasted at least 12 weeks and returned to values close to the starting level within 24 weeks. In the analysis of 13 controlled studies, the effect lasted for up to 12 to 24 weeks; in another review of nine studies, it lasted between 12 and 36 weeks.

Results also differ between individual studies. In one randomised trial, the reduction was still present at week 24 and had returned to the starting level at week 48. In another randomised trial, measurements had not returned to starting values at six months. A meta-analysis comparing surgical and non-surgical methods found that the result of non-surgical methods had partly reversed at six months and had returned to the starting level at 12 months.

The products, doses and injection protocols used in studies differ widely; this is one reason why the duration cannot be reduced to a single number. The most common limitation is that the effect is temporary and the treatment usually needs to be repeated. How long the effect may last for you is discussed at your consultation.

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Limits of This Treatment

Botulinum toxin affects only the muscle-related part of the gum display, and only temporarily. It does not correct an appearance caused by the bone, teeth or gums. In studies, non-surgical methods have also given more limited results when gum display is severe.

A meta-analysis comparing surgical and non-surgical treatments found a similar average reduction in both groups at one month (3.50 and 3.43 millimetres). At six months, however, the reduction had fallen to 0.51 millimetres with non-surgical methods, while it remained at 2.86 millimetres with surgical methods. In the same analysis, non-surgical methods gave better results in mild gum display and surgical methods in severe cases. The researchers stressed that more rigorous studies are needed for more robust results.

The picture is similar for how the smile is perceived. In a study that assessed 26 patients from past records, smile attractiveness increased after treatment in both groups: those treated with botulinum toxin and those who had surgery to move the upper jaw upwards. However, the increase was significantly greater in the surgical group. This is a small, retrospective study; even so, it shows that the two methods do not address the same problem to the same extent.

In practice, these limits can be summed up as follows:

• For vertical excess of the upper jaw, jaw surgery is considered the ideal solution.
• When the gums cover too much of the teeth, the established treatment is directed at the gums and teeth.
• The effect of botulinum toxin wears off on its own; keeping it depends on repeating the treatment.
• There is no standard treatment protocol, and the same dose can give different results in different people.

Which path makes sense for you is decided through the assessment at your consultation and your own decision.

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Orthodontic and Surgical Options

When the cause is not muscle-related, or when gum display is severe, orthodontic (correcting the position of the teeth and jaws), periodontal (gum-focused) and surgical options are considered. These options fall within the specialist fields of dentistry and surgery and need a separate assessment in the relevant field. They are summarised briefly here only so that you can compare them with botulinum toxin.

According to a review that included only randomised trials, orthodontic and surgical methods are effective in reducing gum display: jaw surgery gives permanent results, particularly for vertical excess of the upper jaw, while orthodontic treatments, including methods that take support from the bone (skeletal anchorage), are effective in milder cases. The same review considers minimally invasive methods such as botulinum toxin to be options with temporary but promising results for patients who do not want surgery.

For vertical excess of the upper jaw, surgery is seen as the most suitable option in moderate and severe cases; however, the surrounding anatomical structures and changes in the shape of the nose limit how far the jaw can be moved upwards. Aesthetic crown lengthening is an established method when the gums cover too much of the teeth, and lip repositioning surgery when the upper lip moves too much. For many newly described techniques, however, the evidence is limited to case reports describing individual patients.

According to a review of 16 studies on lip repositioning surgery, this procedure, combined with an intervention targeting the muscle, can be successful for small discrepancies in selected patients; controlled studies are needed on how long it lasts in the long term. When there is more than one cause, this procedure can be combined with methods such as crown lengthening.

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Known Risks

The adverse effects reported after botulinum toxin treatment for a gummy smile are mostly mild and temporary. Even so, because the treatment is given directly into the smile muscles, the most important issue is the balance between the two sides of the smile. The rates below come from other studies; they are not the clinic’s own data and cannot be used to calculate your personal risk.

A review covering nine studies reported a total of 14 adverse effects, all described as mild and temporary. In one randomised trial, a small number of adverse effects were seen. In the 16-patient study that defined the types of gummy smile, two patients had mild adverse effects, which were corrected with additional doses. The summaries of reviews specific to gummy smile do not classify the types of these effects in detail; this is a gap in the available data.

There are broader data on lower face treatments. In a review covering 8,787 people, lip asymmetry and imbalance were reported at a rate of 6.9% after lower face treatments, and these were said to have resolved on their own. According to a recent source on botulinum toxin complications in the face, facial asymmetry and functional problems around the mouth are also usually mild and resolve on their own; however, approaches to managing them are mostly based on low-level evidence.

Unexpected effects have also been reported in individual patients: a detailed case report describes a patient who developed horizontal wrinkles on the upper lip after treatment for a gummy smile; the wrinkles appeared when the lip moved. This is a single case and does not show how often this risk occurs; but it is a reminder that the muscles in this area are closely interwoven. The general risks of botulinum toxin, the spread of the toxin to surrounding areas and situations that need particular care are described in detail on the Botulinum Toxin page.

RELATEDBotulinum Toxin

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